ABS resin is obtained from copolymerizing butadiene, styrene, and acrylonitrile. It has outstanding physical-mechanical performance and is one of the important resins among engineering polymer materials. In ABS resin production, emulsion batch polymerization is widely adopted. First of all, butadiene is polymerized into polybutadiene (hereinafter referred to as PB) latex. Then, PB latex is graft polymerized with styrene and acrylonitrile to form ABS graft polymer powder, which is eventually blended with SAN (binary copolymer of styrene and acrylonitrile) to produce ABS resin granules. Particle size of PB latex greatly affects the performance of ABS product. It has been proven that the best performance of ABS is when particle size of the PB latex is about 300 nm. There are two ways to produce PB latex of large particle size, namely, butadiene direct polymerization and agglomeration. Butadiene direct polymerization, which has various defects, has been replaced by agglomeration gradually. Agglomeration, which is widely used at present, includes the polymerization of PB latex with small particle sizes of approximate 100 nm. A reagent is then used to agglomerate the small particle sized PB latex. After agglomeration, the mean particle size of PB latex becomes more than 300 nm. Then, the agglomerated latex is graft polymerized with styrene and acrylonitrile to form ABS powder. LG Company, Kumho Tire Inc. and Chi Mei Corporation of Taiwan all adopt the method of agglomeration to produce PB latex with a particle size of 300 nm though their polymerization technologies are different from each other. LG Company uses fatty acid soap and abietic acid soap as emulsifying agent to produce small particle-sized PB latex. The time for polymerization lasts 17 hours, and the monomer conversion is up to 90%. Kumho Tire Inc. uses abietic soap as emulsifying agent, and oleic soap is added in the late phase of the reaction to produce small particle-sized PB latex. The time for reaction lasts 20 hours, and the monomer conversion is more than 97%. A Chinese Application No. 94109547.9, in the name of Chi Mei Corporation of Taiwan, China, discloses that sodium lauryl sulfate is used as emulsifying agent to synthesize small particle sized PB latex. The reaction time is 12 hours, and the monomer conversion is up to 94%. A European patent Application having the publication No. EP0650983 in the name of GE Company of USA discloses that only fatty acid soap is used as emulsifying agent. The total reaction time is 14 hours, including 9 hours for reaction at 63° C. and 5 hours for reaction at 71° C. The monomer conversion reaches 100%, and the conversion in extended test is more than 94%.
In addition, the two methods of butadiene direct polymerization and chemical agglomeration are adopted in polybutadiene (PB) polymerization, achieving particle size of the obtained latex of 300 nm. The purpose of chemical agglomeration is to improve the productivity and shorten the reaction time. As the reaction time for PB polymerization is shortened, the exothermic time of PB polymerization is shortened accordingly. Particularly, when the polymerization time is shortened to within 10 hours, the exothermicity will be very fierce, so it is desired that the reaction heat is released evenly during the ten hours. The characteristics of PB polymerization are to show that when the conversion is less than 40%, the reaction heat is released evenly; when the conversion is in the range of 40%˜80%, the reaction heat is released extremely fiercely; when the conversion is more than 80%, the released reaction heat is reduced as monomers are consumed. The present common temperature-controlling curve of PB polymerization in the world indicates a ladder-type ascent curve, and it is necessary to remove heat from the polymerization system, so as to control the temperature. Also, it is required that the system has powerful heat removing conditions to stabilize the temperature. However, it is hard to remove heat from the polymerization reactor, and how to evenly discharge the reaction heat of polymerization is the key to stabilize the fierce heat releasing.